This invention relates generally to a supporting tray for tubular objects and more particularly to a new and novel thermoformed plastic tray that may be used to support fluorescent tubes in an outer corrugated package to minimize tube breakage whenever the outer package is accidentally dropped or handled roughly.
It is common in the industry to package fluorescent lamps in an outer box with a series of inner separations or trays between the lamps to prevent breakage in transit.
Prior to the early 1960's, a common material used for the separating tray was pulp paper as shown in the U.S. Pat. No. 3,143,274, issued Aug. 4, 1964 to Donald G. Maize and assigned to General Electric Company. Various configurations of formed pulp trays were designed thereafter as typified by the U.S. Pat. No. 3,163,312, issued Dec. 29, 1964 to Charles J. Chaplin and assigned to Diamond National Corporation. The pulp trays all tried to minimize tube breakage during handling and shipment of the package containing the fluorescent tubes to the ultimate customer.
With the advent of plastic technology and specialized plastics and forming techniques for those plastics, there were designed fluorescent separation trays to be formed out of plastic. For example the U.S. Design Pat. No. D-202,580 to Hugh R. Weiss and the U.S. Pat. No. 3,223,234, issued on Dec. 14, 1965 to the same inventor typified the use of a plastic tray formed from vacuum molded thin sheets of plastic. These designs and others to follow generally used parallel spaced apart ribs formed in side by side openings to support the fluorescent tubes. The rib supports were generally designed in a semicircular form and ran transverse to the longitudinal direction of the fluorescent tube.
Variations of this type of parallel rib supports can also be seen in the U.S. Pat. No. 3,708,084, issued Jan. 2, 1973, to Kenneth D. Bixler et al and in the U.S. Design Pat. No. D-249,638, issued Sept. 26, 1987 to Gilbert R. Chadbourne.
A variation of this standard type of rib support is shown in the U.S. Pat. No. 4,427,730, issued on Jan. 24, 1984, to Gerald L. Robbins et al and assigned to Keyes Fibre Company. This design was to be used either with molded pulp or foam plastic.
It is known to manufacture one-piece plastic trays out of polyvinyl chloride (PVC) as taught in the U.S. Pat. No. 4,705,170, issued to David E. Creaden on Nov. 10, 1987 and assigned to the Lawrence Paper Company of Lawrence, Kans. Reference should be made to that patent and the patents cited therein for a more detailed discussion of the overall problems encountered in protective packaging in general and in fluorescent tube tray design in particular.
The Creaden patent, while directed primarily to providing de-nesting features to make the tray more adaptable to machine facilities, primarily uses a dense polyvinyl chloride sheet material in the formation of the tray. In addition, the Creaden patent teaches the use of striations on the faces of the fluorescent tube engaging surfaces to obtain the necessary cushioning of the tube. The patent teaches also that the use of cushioning ribs on the tray's underside results in a controlled collapse of the respective elements of the tray. This feature of a controlled collapse is also claimed for certain notches in the tray and is believed to be responsible for the test results obtained by the patentee. In other words, the polyvinyl chloride tray uses a controlled collapse in certain parts of the tray which protects the tubes only on the first impact of a drop of the package. Subsequent impacts can not be protected since the tray does not permit the collapsed portions to spring back or return to their original positions. This is caused partly by the use of polyvinyl chloride (PVC) in the tray, which is a dense material, and partly by design imperfections which will be explained more fully hereinafter.
While prior art type trays were previously made of molded pulp or paperboard, the Creaden invention claims only to be able to equal the support performance of the seriously deficient molded pulp tray. It would be very advantageous to be able to provide far better support performance in a fluorescent tube tray than that obtainable by the Creaden invention. By his own admission in the patent, Creaden claims his tray is only as good as molded pulp trays. To be able to obtain a 30%-50% better performance of a tray in drop tests would appear to be highly supportive of the conclusion that such an improved tray had unique features and was certainly new and novel within the structure of the patent laws.
While the problems of the prior art trays have been only briefly discussed in this section, there will be discussed in greater detail hereinafter how the use of polyvinyl chloride and the particular design of the Creaden tray prevents a better performance. This will be discussed when showing the much improved tray of the applicant's design which, by actual test results, was able to obtain 30%-50% better performance in drop tests.